video doorbell cant find the internet, how to create a network with just 2.4

Three things you can do:

1) Turn on the Guest Network on your Gateway (on the Home Network > Wi-Fi page).  It's always 2.4 GHz only.

2) Temporarily disable the 5 GHz radio (Home Network > Wi-Fi > Advanced Settings... , under 5 GHz Wi-Fi Configuration set Wi-Fi Operation to Off, scroll down and click Save. Set up your device, then turn it back on.  If your device continues to work, this option may be good for you.  Some devices will have problems after 5 Ghz is turned back on.

3) Change the SSIDs for 5 GHz to something else (Network Name under the Home SSID section of  5 GHz Wi-Fi Configuration ).  A lot of people add 5 to the name.  Then you can decide what devices use 5 GHz and which don't by choosing the appropriate SSID.  When you do this, you'll get a warning about fire, floods, and pestilence because of you disabling band steering.  It's really not that bad; only one of those will actually happen at a time.

Hi JefferMC my service is 500 internet fiber, as i not need anything more for my needs, i tried to do it but the app do not allow me, i created a guest network but cant change  to 2.4 GHz, before ATT i had T Mobile 5GB and i did all the change you just mention above, noting work, that why i get ATT because that was the provider i had before and i didnt have problem connecting my motion light outside, I dont know why i have such a hard problem with the video doorbell, this problem is. frustrated that i get to the point to return both video doorbell.

Maybe I am doing something wrong in the set up, i even long in using my regular computer, that how i found this forum.

i created a guest network but cant change  to 2.4 GHz,

If you enabled the guest network on an AT&T gateway, you certainly would not have been able to change it to 2.4 GHz, because it already was 2.4 GHz only.